#include
#include
using namespace std;
int main() {
char s[1000];
cin>>s;
int frequency[256]={0};
for(int i=0;i<strlen(s);i++)
{
frequency[s[i]]++;
}
int max=INT_MIN;
char ans;
for(int i=0;i<256;i++)
{
if(max<=frequency[s[i]])
{
max=frequency[s[i]];
ans=s[i];
}
}
cout<<ans;
}